Photo-polymerizable compositions (as described, for example, in U.S. Pat. Nos. 3,046,127 and 3,549,367) are essentially composed of a photo-initiator, a polymerizable compound and a binder, which become insoluble in solvents by polymerization of the exposed part when exposed to light. This property has been broadly utilized in areas such as sensitive layers of photoresist, lithographic printing plates and various other image recording materials, UV hardenable inks and coatings. For example, U.S. Pat. Nos. 2,760,863 and 2,791,504 disclose use for preparing relief printing plates; U.S. Pat. Nos. 3,060,023, 3,060,024 and 3,060,025 disclose use for producing copies of images; U.S. Pat. Nos. 3,479,185 discloses use for producing a lithographic printing plate; and U.S. Pat. Nos. 3,469,982 and 3,526,504 disclose use for producing photoresists. However, in most photo-polymerizable compositions, organic compounds such as Michler's ketone are used as a photo-initiator. Accordingly, the light sensitivity thereof is at most 10.sup.5 to 10.sup.6 erg/cm.sup.2 and sensitizable light wavelength is limited to a short wavelength range of less than 400 nm. Therefore, their use is limited, because they do not have a sufficient sensitivity to light of, for example, 488 nm and 514.5 nm in visible argon laser at an output of several mW.
On the other hand, silver halide has been broadly used as a photosensitive material of photographic films, because it has a high sensitivity to light. Further, it is known that silver halide containing image recording materials are capable of expanding their spectral sensitivities to a wide wavelength range from ultraviolet light to visible light by using sensitizing dyes such as cyanine dyes or merocyanine dyes. For this reason, it has been proposed to utilize a silver halide emulsion as a photo-initiator of the photo-polymerizable compositions as described in British Pat. No. 866,631.
The photo-polymerizable compositions disclosed in British Pat. No. 866,631 comprise a combination of a silver halide emulsion using a water soluble high polymer (such as gelatin, polyvinyl alcohol, carboxymethyl cellulose, methyl cellulose, starch, polyvinyl pyrrolidone, polyacrylamide or casein, etc.) as a high polymer for dispersion of silver halide, a vinyl monomer and water. Further, British Pat. No. 866,631 has disclosed the application of the compositions to image formation, such as production of relief or lithographic printing plates. These compositions have good sensitivity. However, they have various faults when they are utilized for production of lithographic printing plates or photoresists, because water soluble high polymers are used as a dispersion medium for silver halide. More specifically, when they are applied to a suitable base to form a sensitive layer, the layers becomes adhesive if the humidity is high. Further, when the sensitive material is processed with water or an aqueous developing solution to remove unexposed unpolymerized part after imagewise exposure to light, the images obtained easily swell and can be easily damaged. If the resulting polymer images are used as a lithographic printing plate, ink adhesion to the image parts is inferior and, consequently, distinct printed images cannot be obtained.
Further, when a silver halide emulsion prepared with a hydrophilic high polymer is blended with an oleophilic high polymer binder, distinct printed images can not be obtained or the printing durability deteriorates. This is because the high polymers have inferior compatibility with each other.
When an emulsion is produced with an oleophilic high polymer, undesirable coarse particles are formed or the stability of the emulsion is insufficient because of inferior dispersion.
British Pat. No. 866,631 describes a process for producing photo-polymerizable compositions in a water-in-oil state. In accordance with this process, a silver salt emulsion using gelatin is dispersed in a toluene solution of a monomer (for example, pentaerythritol tetraacrylate) and ethyl cellulose. (But, there is no description relating to examples of image formation using those compositions.) The patent recommends the use of lauryl sulfonate as a dispersing agent in order to carry out good dispersion. However, if a wetting agent such as lauryl sulfonate is added, the strength of images further deteriorates, because the polymer images are easily separated from the base during development.